Substrate, optical fiber connection end member, optical element housing member, and method of fabrication of an optical module and the substrate

ABSTRACT

The present invention provides a substrate, an optical fiber connecting end member, an optical element-housing member, a light module, and a manufacturing method of the substrate. The substrate has a feature that can be stably realizable and having a simple structure and that a light waveguide formed on the substrate surface or an optical element formed thereon can be connected without core alignment to an optical element provided on the optical fiber of the optical fiber connector to be connected to the optical fiber connecting end member. The substrate of the present invention is characterized in steps  5  for positioning being formed on at least one side of the substrate  1  that provides the optical waveguide  4.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a substrate, optical fiber connectingterminal member, optical element housing member, and method offabrication of an optical module and the substrate, and in particular toa substrate, an optical fiber connecting end member, and an opticalelement housing member that can connect without alignment of the coresand at high precision an optical element mounted on an optical waveguideon a substrate or mounted on the substrate to an optical fiber of anoptical fiber connector that is connected to an optical fiber connectingend member or an optical element provided on an optical element housingmember, and a fabrication method for an optical module and a substrate.

2. Description of the Related Art

In broadband optical communication networks and high-speed datatransmission between computers, parallel optical modules and multiplecore optical transmission and reception modules and the like arenecessary. An increasingly higher quality and decreasing cost arerequired for these modules, and reducing the number of parts,simplification of the module structure, and decreased energy consumedduring the fabrication process and the like are indispensable for thefurther improvement.

When an optical module is assembled on the device, an ordinary pigtailmodule entails the problem of processing of the optical fiber's excesslength, which means that extra space is necessary in order toaccommodate the optical fiber mounted in the optical module. Therefore,using an optical module with an attached optical fiber receptacle thatcan be detached from the optical fiber is desired.

In order to apply the multiple core optical fiber receptacle structureto this optical module, it is necessary to align with high precision therelative positions of a guide pin or a guide pin insertion hole, whichare used to connect to the multiple core optical fiber connector, andthe optical axis of the optical module.

Active alignment, for example, can be considered to be such a corealignment method. In this alignment method, positions are adjusted bymoving the optical module and the receptacle relative to each otherwhile the optical module is emitting light, so that the light is moststrongly incident on the optical fiber. Then this receptacle is attachedto the optical module.

However, in this active alignment, because the position adjustment ofthe optical module and the receptacle must be carried out using aprecision manual operation, the optical module becomes a factor thatcauses a high cost. In order to decrease the cost of the optical module,this kind of alignment by a precision manual operation should beavoided, and an optical module having a structure that can be assembledwithout core alignment is required.

FIG. 15 is an exploded perspective view showing the optical waveguidepart disclosed in Japanese Unexamined Patent Application, FirstPublication, No. Hei 8-248269, which is one example of a multiple coreoptical module having a structure whose assembly does not require corealignment, and FIG. 16 is a partial cross-sectional perspective view ofthe same. In this optical waveguide path, both ends 100 a and 100 b ofan optical waveguide body 100 are respectively inserted into and fixedin separate connecting end members 101 and 101.

The optical waveguide body 100 provides a substrate 102, a cladding 103,and an optical waveguide core 104 comprising a plurality of cores 104 a.On the upper surface of the cladding 103, two V-shaped grooves 105 a and105 b are formed on respective sides of the optical waveguide core 104.

On the connecting terminal member 101, a through hole 107 and guide pininsertion holes 108 a and 108 b that pass from the one end surface 106 athereof to the other end surface 106 b thereof are formed, and in thethrough hole 107, V-shaped projections 109 a and 109 b that engage theV-shaped grooves 105 a and 105 b are formed.

In this optical waveguide part, the one end 100 a of the opticalwaveguide body 100 is inserted into the through hole 107 of theconnecting end member 101 such that the V-shaped grooves 105 a and 105 bthereof are engaged with the V-shaped projections 109 a and 109 b. Theend surface of each core 104 a of the light guiding core 104 and the endsurface 106 a of the connecting end member 101 are made flush to eachother, and while being held in this state, both are attached and fixed,and thereby the optical waveguide body 100 can be fixed to theconnecting end member 101 without core alignment.

However, in this optical waveguide part, because the optical waveguidebody 100 is inserted into the connecting end member 101 while theV-shaped grooves 105 a and 105 b are engaged in the V-shaped projections109 a and 109 b, there is the problem that the V-shaped grooves 105 aand 105 b and the V-shaped projections 109 a and 109 b can be easilybroken.

Thus, an optical waveguide that avoids this problem is disclosed inJapanese Unexamined Patent Application, First Publication, No. Hei8-248269.

As is shown in FIG. 17, this optical waveguide part is structured sothat substantially identically shaped V-shaped grooves 111 a and 111 bare formed at positions in the through hole 107 of the connecting endmember 101 opposite to the V-shaped grooves 105 a and 105 b of theoptical waveguide body 100, and the respective optical fibers 112 andthe like are interposed between the V-shaped grooves 105 a and 111 a andbetween the V-shaped grooves 105 b and 111 b.

In addition, the optical waveguide apparatus disclosed in JapaneseUnexamined Patent Application, First Publication, No. Hei 9-105838, isanother example that avoids the problem described above.

As is shown in FIG. 18, in this optical waveguide apparatus, theconnecting end members 202 and 203, which surround and engage both sidesurfaces and the upper surface 210 of the waveguide chip 201 by theengaging recess 216, engage and fasten the connecting end surfaces 225 aand 225 b of the waveguide chip 201 that forms the core 206 and the clad205 on the substrate 210, to form the optical waveguide apparatus shownin FIG.

In this optical waveguide apparatus, both end sides of the optical fiber209 are sandwiched between the V-shaped grooves 208 a and 208 b formedon both sides of the upper surface 210 of the waveguide chip 201 and theinverse V-shaped grooves 214 and 215 formed at positions correspondingto the V-shaped grooves 208 a and 208 b of the engagement recess 216 ofthe connecting end members 202 and 203, and thereby the positioning ofthe waveguide chip 210 and the connecting end members 202 and 203 iscarried out.

However, in the conventional optical waveguide part and the opticalwaveguide apparatus described above, an optical fiber, which is a verysmall part, must be aligned with and mounted on a V-shaped groove and aninverse V-shaped groove, and there is the problem that obtaining highprecision is difficult.

In addition, the problem with the optical waveguide part and opticalwaveguide apparatus is the precision of the V-shaped grooves. Thus, amethod that improves the precision of the V-shaped groove is disclosedin Japanese Unexamined Patent Application, First Publication, No. Hei9-105838.

This method includes a method of forming a V-shaped groove using machineprocessing and a method of forming a rectangular groove by etchingprocessing, but generally, in these methods, achieving sub-micron levelprecision is difficult, and applying these methods to single modeoptical fiber arrays presents problems.

SUMMARY OF THE INVENTION

In consideration of the above described problems, it is an object of thepresent invention to provide an optical waveguide on a substrate or anoptical element mounted on a substrate and an optical fiber of anoptical fiber connector connected to an optical fiber connecting endmember or an optical element provided on an optical element housingmember that can be connected without core alignment and at highprecision, and furthermore, has a simple structure, and a substrate thatcan be stably realized, and an optical fiber connecting end member, anoptical element housing member, and a fabrication method of an opticalmodule and a substrate.

In order to resolve the problems described above, the present inventionuses the following type of substrate, optical fiber connecting endmember, optical element housing member, and fabrication method for anoptical module and the substrate.

Specifically, in a substrate that provides an optical waveguide,according to a first aspect of the present invention, the substrate ischaracterized in steps for positioning being formed on at least one sideof this substrate.

In a second aspect of the present invention, this substrate according tothe first aspect is characterized in an optical element mounted on theoptical waveguide which is connected thereto.

In a third aspect of the present invention, the substrate according tothe first and second aspects is characterized in inclined grooves thatincline relative to the propagation direction of the light being formedon the optical waveguide, and a light reflecting device that reflectsthe light propagated through the optical waveguide to the outside of theoptical waveguide being provided.

In a fourth aspect of the present invention, the substrate according tothe first and second aspects is characterized in inclined grooves thatincline relative to the propagation direction of the light being formedon the optical waveguide, and an optical wavelength selecting devicethat selects the light having a wavelength within a desired range fromthe light propagated through the optical waveguide and extracts it tothe outside of the optical waveguide being provided on the inclinedgroove.

In a fifth aspect of the present invention, in a substrate on whichoptical elements are mounted, the substrate is characterized in stepsfor positioning being formed on at least one side of this substrate.

In a sixth aspect of the present invention, in an optical fiberconnecting end member having formed therein a hole for accommodating andfixing one end of the substrate and optically connecting the substrateto the optical fiber, an optical fiber connecting end member ischaracterized in steps for positioning the substrate being formed on thesubstrate in the hole.

In a seventh aspect of the present invention, in an optical elementhousing member having formed therein a hole for accommodating and fixingone or the other end of the substrate and optically connecting thesubstrate to the optical element, the optical element housing member ischaracterized in steps for positioning the substrate being formed in thehole.

In an eighth aspect of the present invention, the optical module ischaracterized in providing a substrate according to any one of the firstthrough fifth aspects and the optical fiber connecting end memberaccording to the sixth aspect and/or the optical element housing memberaccording to the seventh aspect.

In a ninth aspect of the present invention, in the optical moduleaccording to the eighth aspect, an optical module is characterized intwo optical fiber connecting end members being disposed opposite to eachother so as to sandwich the optical element housing member, and thesubstrate on which the optical fiber connecting end member isaccommodated and fixed and the optical element of the optical elementhousing member being optically connected.

In a tenth aspect of the present invention, in the optical moduleaccording to the eighth and ninth aspects, the optical module ischaracterized in the substrate being pressed against the optical fiberconnecting end member by the urging force of a flexible member.

In an eleventh aspect of the present invention, a fabrication method forthe substrate according to any of the first thorough fifth aspects, ischaracterized in steps for positioning being formed on at least one sideof the substrate by anisotropic etching.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an exploded perspective drawing showing the optical moduleaccording to the first aspect of the present invention.

FIG. 2 is a cross-sectional drawing showing the optical module accordingto the first aspect of the present invention.

FIG. 3 is an exploded perspective drawing showing the optical moduleaccording to the second aspect of the present invention.

FIG. 4 is an exploded perspective drawing showing the optical moduleaccording to the third aspect of the present invention.

FIG. 5 is an exploded perspective drawing showing the optical moduleaccording to the fourth aspect of the present invention.

FIG. 6 is an exploded perspective drawing showing the optical moduleaccording to the fifth aspect of the present invention.

FIG. 7 is a cross-sectional drawing showing the optical module accordingto the sixth aspect of the present invention.

FIG. 8 is an exploded perspective drawing showing the optical moduleaccording to the seventh aspect of the present invention.

FIG. 9 is an enlarged perspective drawing showing the Si sub-mount ofthe optical module according to the seventh embodiment of the presentinvention.

FIGS. 10A and 10B are cross-sectional drawings showing an example of thecompensated step of an optical module according to a seventh embodimentof the present invention.

FIG. 11 is a perspective drawing showing the optical module according tothe eighth aspect of the present invention.

FIG. 12 is an exploded perspective drawing showing the optical moduleaccording to the ninth aspect of the present invention.

FIG. 13 is cross-sectional drawing showing a modified example of theoptical module according to the ninth aspect of the present invention.

FIGS. 14A to 14D are process drawings showing the fabrication method forthe optical module according to the tenth embodiment of the presentinvention.

FIG. 15 is an exploded perspective drawing showing a conventionaloptical waveguide part.

FIG. 16 is a partial cut-away perspective drawing showing a conventionaloptical waveguide part.

FIG. 17 is a cross-sectional drawing showing another example of aconventional optical waveguide part.

FIG. 18 an exploded perspective drawing showing a conventional opticalwaveguide apparatus.

FIG. 19 is a perspective drawing showing a conventional opticalwaveguide apparatus.

DETAILED DESCRIPTION OF THE INVENTION

Each embodiment of the optical module and the fabrication method for thesame of the present invention will be explained referring to thefigures.

First Embodiment

FIG. 1 is an exploded drawing showing the optical module according tothe first embodiment of the present invention, and FIG. 2 is across-sectional drawing of the same optical module. In the figures,reference numeral 1 is an optical waveguide substrate (a substrate thatprovides an optical waveguide), and reference numeral 2 is an opticalfiber connecting end member that accommodates and fixes the end of theoptical waveguide substrate 1.

In the optical waveguide substrate 1, a silicon optical waveguide 4,which has a multiple core structure wherein a plurality of cores 4 a areburied in the clad 4 b, is formed on a rectangular Si substrate 3, andon both sides of the upper surface of this Si substrate 3, highprecision steps 5 and 5 are formed along the longitudinal directionthereof by anisotropic etching of the Si.

One end surface 11 a of the plastic housing 11 of the optical fiberconnection end member 2 is flattened by grinding, and guide pininsertion holes 12 and 12 into which guide pins are inserted while beingconnected to the optical fiber connector and a through hole 13 foraccommodating and fixing the end surface of the optical waveguidesubstrate 1 are formed so as to pass from one end surface 11 a to theother end surface 11 b. In this though hole 13, a cavity 14 that openson the bottom surface of the housing 11 is formed, and at the same time,on the inside thereof, steps 15 and 15 are formed so as to have a shapethat is complementary to the steps 5 and 5, which are formed on theoptical waveguide substrate 1. The diameter of these guide pin insertionholes 12 is, for example, 0.7 mm.

The optical fiber connecting end member 2 is formed by transfer moldingsuch that the relative positions of the steps 15 and 15 and the guidepin insertion holes 12 and 12 have a sufficient precision. In addition,the angle of inclination of the steps 5 and 5 and the steps 15 and 15is, for example, 45 degrees.

In this optical module, after inserting the optical waveguide substrate1 into the through hole 13 of the optical fiber connecting end member 2,using a pressing member and the like, this optical waveguide substrate 1is pressed from the cavity 14 towards the upper surface of the opticalfiber connection end member 2, and the optical waveguide substrate 1 isattached and fixed to the optical fiber connection end member 2 by anepoxy glue and the like.

At this time, the steps 5 and 5 of the optical waveguide substrate 1 areautomatically aligned at high precision with the steps 15 and 15 of theoptical fiber connection end member 2.

Due to this optical module, along the longitudinal direction on bothsides of the optical waveguide substrate 1, the steps 5 and 5 areformed, and in the though hole 13 of the optical fiber connection endmember 2, the steps 15 and 15 are formed so as to have a shape that iscomplementary to the steps 5 and 5, and thus, when this opticalwaveguide substrate 1 is anchored and fastened to the optical fiberconnection end member 2, these steps 5 and 5 are aligned with each otherby the steps 15 and 15, and high precision positional alignment becomepossible.

Thereby, the relative positions of the core 4 a of the optical waveguidesubstrate 1 and the guide pin insertion holes 12 and 12 of the opticalfiber connection end member 2 can be aligned at high precision withoutcore alignment, and thus the core 4 a of the optical waveguide substrate1 and the optical fiber of the optical fiber connector connected to theoptical fiber connection end member 2 can be connected at high precisionand without core alignment.

Second Embodiment

FIG. 3 is an exploded perspective drawing showing the optical moduleaccording to the second embodiment of the present invention, and thepoint of difference between the optical module according to thisembodiment and the optical module according to the first embodimentdescribed above is that, in contrast with the first embodiment in whichthere is only a structure in which a silicon optical waveguide 4 isformed such that the optical waveguide substrate 1 has a plurality ofcores 4 a buried in a clad 4 b on the Si substrate 3, in the opticalmodule according to the present embodiment, a semiconductor laser(optical element) 21 for inputting a laser beam into the opticalwaveguide 4 is mounted on the Si substrate 3, thereby making a hybridlight condensing module.

In this optical module, in addition to the optical waveguide 4, asemiconductor laser 21, which is an optical element, is mounted on theSi substrate 3, and thus the optical module can be hybridized.

Third Embodiment

FIG. 4 is an exploded perspective drawing showing the optical moduleaccording to the third embodiment of the present invention, and thepoint of difference between the optical module according to thisembodiment and the optical module according to the first embodiment isthat, in contrast to the first embodiment in which there is a structurein which a silicon optical waveguide 4 is formed such that the opticalwaveguide substrate 1 has a plurality of cores 4 a buried in a clad 4 bon the Si substrate 3, in the optical module according to the presentembodiment, the steps 5 and 5, like those of the first embodiment, areformed using anisotropic etching on both sides of a Si sub-mount (asubstrate providing an optical element) 31 on which is mounted asemiconductor laser 21, this Si sub-mount 31 is inserted in the opticalfiber connecting end member 2, position alignment is carried out suchthat the light emitting surface of the semiconductor laser 21 is flushwith the end surface 11 a of the optical fiber connection end member 2,and this Si sub-mount 31 is fixed to the optical fiber connecting endmember 2 by an adhesive and the like.

In this optical module, the semiconductor laser 21 and the externaloptical fiber (not illustrated) are directly linked without interposingan optical waveguide. In addition, the semiconductor laser 21 isautomatically mounted at high precision with a predetermined position onthe Si sub-mount 31 by self-alignment using solder bumps.

According to this optical module, due to having this type of structure,a short optical fiber and optical waveguide do not need to be mounted inthe optical module, the number of parts can be reduced, fabrication costcan be reduced, and the price made inexpensive.

In addition, because the number of optical joints becomes few, thereflection and linking loss in the optical linking part can beattenuated. In addition, the linking between the optical element and theoptical fiber can be attenuated without aligning the optical axes.

Moreover, this optical module can be structured such that not only thesemiconductor laser 21, but other light emitting elements, lightreceiving elements such as photodiodes (PD) and avalanche photodiodes(APD), or a plurality of optical elements are mounted. In addition, itcan be structured so that the vicinity of the light emitting elementssuch as the semiconductor laser 21 or the light receiving elements suchas the photodiode (PD) and the avalanche photodiodes (APD) can be sealedby a transparent resin.

In the case of being sealed in a transparent resin, the resin extrudesto the outside from the through hole 13 of the optical fiber connectingend member 2, but this extrusion resin can be cut off and flattened bygrinding. In addition, if the resin sealing is carried out in advancewhile the opening on the optical fiber side of the through hole 13 ofthe optical fiber connecting end member 2 is covered by a glass plateand the like, a flat end surface can be obtained without requiringgrinding. In addition, applying a non-reflecting coating to the glassplate is effective as a reflection prevention measure.

Furthermore, mounting electrical components such as the driver for alaser or preamps for light reception elements on the Si sub-mount 31 iseffective in high-speed operation of the optical module because thewiring length between these electrical components and optical elementscan be shortened.

Fourth Embodiment

FIG. 5 is an exploded perspective drawing showing an optical moduleaccording to the fourth embodiment of the present invention, and theoptical module of the present embodiment is structured such that the Sisub-mount 42 on which the semiconductor laser 21 is mounted is insertedinto the optical element housing member 41 by a self-aligning methodusing solder bumps.

Like the optical fiber connection end member 2, a through hole 43 andsteps 44 are formed on this optical element housing member 41, and steps45 having a shape complementary to the steps 44 are formed on both sidesof the Si sub-mount 42.

In this optical module, the precision of the attachment position of theSi sub-mount 42 and the optical element housing member 41 is attained byaligning and fixing the steps 45 formed on the Si sub-mount 42 and thesteps 44 formed on the optical element housing member 41.

Next, the end of the optical waveguide substrate 1 is inserted into theoptical fiber connection end member 2. At this time, like the firstembodiment, the optical waveguide substrate 1 and the optical fiberconnection end member 2 are positioned and fixed. Next, the other end ofthe optical waveguide substrate 1 is inserted into the through hole 43of the optical element housing member 41. At this time, the precision ofthe connection position of the optical waveguide substrate 1 and theoptical element housing member 41 can be attained by aligning and fixingthe steps 5 formed on the Si substrate 3 and the steps 44 formed on theoptical element housing member 41. In addition, the precision of theposition of the semiconductor laser 21 on the Si sub-mount 42 can beattained by being aligned by the above-described self-alignment.

According to the above, the steps 5 formed on the optical waveguidesubstrate 1 and the steps 44 formed on the optical element housingelement 41 are aligned and fixed, and thereby the connection between thesemiconductor laser 21 and the optical waveguide substrate 1 can beattained without alignment. This semiconductor laser 21 is linked to theexternal optical fiber via the optical waveguide 4.

In the second embodiment described above, the end face 11 a of theoptical fiber connecting end member 2 must be ground while thesemiconductor laser 21 is mounted on the optical waveguide substrate 1,but in the present embodiment, the semiconductor laser 21 can beassembled after grinding the end surface 11 a of the optical fiberconnecting end member 2 beforehand. Therefore, this structure iseffective in the case the optical elements such as the mountedsemiconductor laser 21 should not be subject to vibration duringgrinding.

Fifth embodiment

FIG. 6 is an exploded perspective drawing showing the optical moduleaccording to the fifth embodiment of the present invention. The opticalmodule according to this embodiment is structured such that a Sisub-mount 52 on which a semiconductor optical amplifier 51 is mounted isinserted into an optical element housing member 41.

Steps 53 that have a shape complementary to those of the steps 44 of theoptical element housing member 41 are formed on both sides of this Sisub-mount 52.

The precision of the attachment position between the Si sub-mount 52 andthe optical element housing member 41, like the fourth embodiment, canbe attained by aligning and fixing the steps 53 formed on the Sisub-mount 52 and the steps 44 formed on the optical element housingmember 41.

In addition, the precision of the position of the semiconductor opticalamplifier 51 on the Si sub-mount 52 is attained by self-alignment.

Next, two optical connecting end members 2 having optical waveguidesubstrates 1 inserted and fixed are prepared, these are disposedopposite to each other so as to sandwich the optical element housingmember 41, and the respective ends of the optical waveguide substrates 1are inserted from both sides into the through hole 43 of the opticalelement housing member 41. Because the other ends of the respectiveoptical waveguide substrates 1 are inserted and fixed in the opticalconnecting end member 2, they can be connected to external opticalfibers.

The precision of the attachment position of the optical element housingmember 41 and the optical waveguide substrates 1 and 1, and theprecision of the attachment position of the optical waveguide substrate1 and the optical fiber connecting end member 2 is attained in the samemanner as the optical module according to the fourth embodiment.

Sixth Embodiment

FIG. 7 is a cross-sectional drawing showing the optical module accordingto the sixth embodiment of the present invention, and the optical moduleaccording to the present embodiment has a diagonal groove 55 formed onthe optical waveguide 4 of the optical waveguide substrate 1, the mirror56 is inserted into the diagonal groove 55, and then the light receivingelement 58 is mounted on bumps 57.

In this optical module, the light that propagates through the opticalwaveguide 4 is reflected by the mirror 56, and is incident on the lightreceiving element 58.

Here, when the mirror is a wavelength selection film, in the case that amultiplexed optical signal propagates through the optical waveguide 4,the light can be received by selectively extracting a specificwavelength among these optical signals.

In addition, a plane light emitting laser can be mounted instead of thelight receiving element 58. Thereby, a light transmitting module using aplane light emitting laser can be made.

Seventh Embodiment

FIG. 8 is an exploded perspective drawing showing an optical moduleaccording to the seventh embodiment of the present invention, and FIG. 9is an enlarged perspective drawing showing the Si sub-mount of theoptical module. In the optical module according to the presentembodiment, the semiconductor laser 21 and the plane light receivingtype light receiving element 58 are mounted on the Si sub-mount 61without alignment and at high precision by self-alignment.

In this Si sub-mount 61, a plurality (two in this case) of partitionedSi substrates 63 a and 63 b are attached to a ceramic plate 62, and anelectromagnetic shield plate 64 comprising an iron plate is providedbetween these Si substrates 63 a and 63 b. Steps 65 are respectivelyformed on the ends of the mutually separated sides of the Si substrates63 a and 63 b.

In addition, on the Si substrate 63 a on which the light receivingelement 58 is mounted, a V-shaped groove mirror 66 is formed byanisotropic etching. A flat micro-lens 68 is attached over the throughhole 13 of the optical fiber connecting end member 2 into which this Sisub-mount 61 is inserted. The V-shaped groove mirror 66 can be formed atthe same time that the steps 65 are formed on the Si substrate 63 a.

In this optical module, the shape of the semiconductor laser 21 and thelight receiving element 58 have, for example, a 300 μm angle and athickness of 100 μm, and the solder bumps 57 for mounting these on theSi sub-mount 61 preferably use a solder having as a main componentAu—Sn. The shape of these solder bumps 57 has, for example, a width of25 μm, a length of 140 μm, a height of 15 μm, with four bumps perelement.

In this optical module, because the V-shaped mirror 66 is formed, a stepat the point of emission of the semiconductor laser 21 and the point ofincidence on the light receiving element 58 is produced, but this stepcan be compensated by attaching the flat micro-lens 68 and providing anoffset for the height at the center of the lens. This means that, asshown in FIG. 10A, the light emitted from the semiconductor laser 21passes directly through the flat micro-lens 68, and is concentrated onthe optical fiber.

In addition, as shown in FIG. 10B, the light that progresses towards thelight receiving element 58 is refracted downwards by the flat micro-lens68 offset from the optical axis, and then is incident on the lightreceiving element 58 by being refracted upward by the V-shaped mirror66.

Due to being structured in this manner, the electrical cross-talk thatoccurs between the semiconductor laser 21 and the signal lines of thelight receiving element 58 can be attenuated.

Eighth Embodiment

FIG. 11 is a perspective drawing showing the optical module according tothe eighth embodiment of the present invention. The optical moduleaccording to the present embodiment is formed such that two Sisub-mounts 31 a and 31 b are inserted and fixed in a through hole 74 ofan optical fiber connecting end member 73. A flat micro-lens 75 isattached to this through hole 74.

The semiconductor laser 21 is mounted on the first Si sub-mount 31 a,and the plane light receiving type light receiving element 69 is mountedon the second Si sub-mount 31. A V-shaped groove mirror 67 is formedbelow the light receiving element 69. In addition, a flat spring 76 isprovided between the two Si sub-mounts 31 a and 31 b.

The steps 5 are respectively formed on the first and second Sisub-mounts 31 a and 31 b, and the steps 15 are respectively formed onthe optical fiber connecting end member 73, and these steps 5 and 15 arealigned, positioned, and anchored.

In this manner, by separating the semiconductor laser 21 and the Sisub-mount on which the light receiving element 69 is mounted, the gap ofthe guide pin insertion hole 12 becomes narrow, and compared to the casewhere the Si sub-mount 31 is disposed between the two guide pininsertion holes 12, there is extra free mounting surface. In addition,the electrical cross-talk that occurs between the semiconductor laser 21and the signal lines of the light receiving element 69 is attenuated.

In this optical module, a flat spring 76 is provided between the two Sisub-mounts 31 a and 31 b, and the respective steps 5 are pressed againstthe steps 15 of the optical fiber connecting end member 73, and therebythese members can be reliably and easily positioned and anchored.

Ninth Embodiment

FIG. 12 is an exploded perspective drawing showing an optical moduleaccording to a ninth embodiment of the present invention. In the opticalmodule according to the present embodiment, a plane light emittingsemiconductor laser 82 and a plane input type light receiving element 83are mounted on the Si sub-mount 81, and in proximity thereto, the steps84 are formed. In addition, steps 86 that have a shape complementary tothe steps 84 are also formed on the optical fiber connecting end member85.

The precision of the position of these optical elements on the Sisub-mount 81 is attained using passive alignment by aligning markers.

In this optical module, the optical fiber connecting end member 85 ispositioned and fixed with high precision on the Si sub-mount 81 byaligning the steps provided on both sides.

In this embodiment, the optical axes of the plane light emittingsemiconductor laser 82 and the plane input type light receiving element83 are perpendicular relative to the Si sub-mount 81, and thus the guidepin insertion holes 12 are formed so as to be perpendicular to the Sisub-mount 81.

FIG. 13 is a cross-sectional figure showing a modified example of theoptical module of the present embodiment, and formed so that the Sisub-mount 81 is positioned and fixed in the lower part of the opticalfiber connecting end member 85 and a flat micro-lens 75 is positionedand fixed in the upper part of the same.

Tenth Embodiment

FIG. 14 is a process diagram showing the fabrication method of theoptical module according to a tenth embodiment of the present invention.First, as shown in FIG. 14A, an optical waveguide layer 92 comprisingsilicon is formed on the Si substrate 91. Here, the thickness of the Sisubstrate 91 is 0.8 mm, and on this Si substrate 91, the opticalwaveguide layer 92 is deposited by chemical vapor phase deposition(CVD). In addition, the cross-sectional angle of the cores 4 a of theoptical waveguide is a 5 μm, and the thickness of the clad 4 b above andbelow the cores 4 a is 15 μm. The gap between cores 4 a is, for example,250 μm, and 12 cores 4 a are formed on one optical waveguide substrate.

Next, as shown in FIG. 14B, the unnecessary portion of the opticalwaveguide layer 92 is removed by etching, and the optical waveguide 4 isformed. This etching is carried out using 16 buffered hydrofluoric acid.

Next, as shown in FIG. 14C, the steps 5 are formed on both sides of theoptical waveguide 4 by anisotropic etching of the Si substrate 91. Thisanisotropic etching is carried out using a potassium hydroxide (KOH)solution.

The thickness of the etched part of the Si substrate 91 is 150 μ, thewidth is about 300 μm, and the angle of the inclined surface caused bythe etching is 54.7 degrees with respect to the Si substrate surface.

Finally, as shown in FIG. 14D, the optical waveguide substrate 1 isformed by dicing the Si substrate 91.

Moreover, the Si sub-mount 31 can be formed by a method in line withthis one.

Above, each embodiment of the optical module and the fabrication methodthereof of the present invention have been explained referring to thefigures. However, the specific structure is not limited to theseembodiments, and modifications of the design are possible that do notdepart from the gist of the present invention.

For example, a structure can be provided wherein a flexible member suchas a flat spring is provided on the optical fiber connecting end member2, and due to the urging force of this flexible member, the opticalwaveguide substrate 1 is pushed towards the inside of the through hole13 of the optical fiber connecting end member 2. Thereby, the alignmentof the optical waveguide substrate 1 and the optical fiber connectingend member 2 can be carried out more easily.

In addition, by providing the end surface of the optical fiberconnecting end member 2 with an inclined surface, the influence ofreflection at the connecting part between the optical fiber and theoptical waveguide 4 can be attenuated.

In addition, at the time the optical waveguide substrate 1 is insertedinto the through hole 13 of the optical fiber connecting end member 2,the end surface of the optical waveguide substrate 1 is attachedprotruding farther than the optical fiber connecting end member 2, thenit is ground, and subsequently the end surface of the optical waveguide4 can be finished protruding only slightly from the end surface 11 a ofthe optical fiber connecting end member 2, and when the connection withthe optical fiber is carried out, a physical connection can be attained,and the influence due to reflection can be attenuated.

In addition, in the case that there is concern about damage to the endsurface of the optical waveguide 4, when the optical waveguide substrate1 is inserted into the optical fiber connecting end member 2, the endsurface of the optical waveguide substrate 1 is attached and fixed bybeing pulled by the end face 11 a of the optical fiber connecting endmember 2, and then the end surface of the optical waveguide substrate 1is filled with transparent filler, and thereby the end surface of theoptical waveguide 4 can be protected.

In addition, in the case that the Si sub-mount on which the opticalelement is mounted is inserted into the optical element housing member41 or the optical fiber connecting end member 2, by sealing the Sisub-mount 31 and the optical element by a transparent resin and thelike, the reliability of the optical module can be guaranteed.

As explained above, according to the substrate of the present invention,steps for positioning are formed on at least one side thereof, and thuswhen accommodating one end of the substrate in the hole of an opticalfiber connecting end member and/or in the optical element housingmember, a high degree of precision can be attained simply by themechanical positioning of the relative positions of the substrate andthe optical fiber connecting end member and/or the optical elementhousing member. Therefore, the optical waveguide and optical element ofthe substrate can be aligned with the optical axes of the optical fiberof the optical fiber connecting end member and/or the optical element ofthe optical element housing member without the optical elements havingto emit light.

In addition, inclined grooves that incline towards the propagationdirection of the light are formed on the optical waveguide, and a lightreflecting device that reflects light propagating through the opticalwaveguide to the outside of the optical waveguide is provided on theinclined groove, and thus the light propagating through the opticalwaveguide can be easily extracted to the outside of the opticalwaveguide.

In addition, inclined grooves that incline towards the propagationdirection of the light are formed on the optical waveguide, and a lightselecting device is provided that selects light having a wavelength in adesired range from the light propagating through the optical waveguideand extracts it to the outside of the optical waveguide, and thus in thecase that wavelength multiplexed light signals are propagating along theoptical waveguide, a certain range of wavelengths can be extracted fromthis light signal, and the light can be received.

According to the optical fiber connecting end member of the presentinvention, because steps for positioning the substrate are formed in ahole that accommodates and fixes one end of the substrate, when the oneend of the substrate is accommodated in the hole of the optical fiberconnecting end member, a high degree of precision can be attained simplyby the mechanical positioning of the relative positions of the substrateand the optical fiber connecting end member. Therefore, the optical axesof optical waveguide and optical element of the substrate can be alignedwith that of optical axis of the optical fiber of the optical fiberconnecting end member without the optical elements having to emit light.

According to the optical element housing member of the presentinvention, because steps for positioning the substrate are formed in ahole that accommodates and fixes one end of the substance, when the oneend of the substrate is accommodated in the hole of the optical fiberconnecting end member, a high degree of precision can be attained simplyby the mechanical positioning of the relative positions of the substrateand the optical fiber housing member. Therefore, the optical axes of theoptical waveguide and optical element of the substrate can be alignedwith those of the optical fiber of the optical fiber housing memberwithout the optical elements having to emit light.

According to the optical module of the present invention, because theoptical fiber connecting end member and/or the optical element housingmember of the present invention are provided, a high degree of precisioncan be attained simply by the mechanical positioning of the relativepositions of the substrate and the optical fiber connecting end memberand/or the optical element housing member. Therefore, the optical axesof optical waveguide and optical element of the substrate can be alignedwith those of the optical fiber of the optical fiber connecting endmember and/or the optical element of the optical element housing memberwithout the optical elements having to emit light.

In addition, because the substrate is urged towards the optical fiberconnecting end member by the urging force of a flexible member, thealignment of the steps of the substrate and the optical fiber connectingend member can be carried out more easily.

According to the fabrication method of the substrate of the presentinvention, because a step for positioning is formed on at least one sideof the substrate by anisotropic etching, a high precision step can beeasily formed on the substrate.

1. An optical module comprising: an elongated optical waveguide havingmultiple cores buried in a clad; a rectangular-shaped silicon opticalwaveguide substrate, on which said optical waveguide is mounted, andalong each side edge of an upper surface of which a high precision stepis formed extending in a longitudinal direction of the waveguidesubstrate; and an optical fiber connecting end member having a holetherethrough for accommodating and fixing an end surface of the opticalwaveguide substrate, the hole having a top surface, a bottom surface, afirst side surface, and a second side surface, wherein: a step is formedon the top surface of the hole, along each side surface of the hole, soas to fit the high precision steps on the waveguide substrate when thewaveguide substrate is inserted in the hole, and said end member has acavity that opens from the bottom surface of the hole to the bottom ofsaid end member, permitting said substrate to be pressed toward the topsurface of the hole so as to align the high precision steps on saidsubstrate with the steps of the hole.
 2. An optical module according toclaim 1, further comprising an optical element mounted on and connectedto said optical waveguide.
 3. An optical module according to claim 1wherein: an inclined groove, that inclines relative to the longitudinaldirection of the optical waveguide, is formed on said optical waveguide,said optical module further comprises a light reflecting devicepositioned in the inclined groove, to reflect light propagated alongsaid optical waveguide to the outside of said optical waveguide.
 4. Anoptical module according to claim 1 wherein an inclined groove, thatinclines relative to the longitudinal direction of the opticalwaveguide, is formed on said optical waveguide, and said optical modulefurther comprises an optical wavelength selecting device range from thelight propagated through said optical waveguide and extracts theselected light to the outside of said optical waveguide.
 5. An opticalmodule according to claim 1, further comprising an optical elementmounted on said waveguide substrate and optically connected to saidoptical waveguide.
 6. An optical waveguide according to claim 1, whereinsaid end member has guide pin insertion holes extending into one endthereof, for insertion of guide pins.
 7. An optical module according toclaim 1, wherein said substrate is affixed to said end member with anepoxy glue.
 8. An optical element housing member comprising a bodymember having a longitudinally extending hole therethrough foraccommodating an end of a substrate and optically connecting thesubstrate to an optical element, wherein: the hole has a top surface, afirst side surface, and a second side surface, a step for positioningthe substrate is formed on the top surface of the hole, along eachlongitudinally extending side surface of the hole, and said body memberincludes a cavity that opens from the bottom surface of the hole to thebottom of said body member, permitting the substrate to be pressedtoward the top surface of the hole so as to align steps on the substratewith the steps of the hole.
 9. An optical element housing memberaccording to claim 7, wherein said body member includes guide pininsertion holes extending into one end thereof, for insertion of guidepins.